Babies exposed to traces of peanut protein in house dust may have a higher risk of peanut allergy researchers say. In a new UK study, published online in the Journal of Allergy and Clinical Immunology, exposure to peanut protein in house dust doubled the chance of having a peanut allergy. In children who have eczema, the risk of having peanut allergy was even higher.

Around 2% of school children in the UK are allergic to peanuts.  Researcher Helen Brough, from the department of Pediatrics allergy at King’s College London and colleagues from the University of Manchester and the University of Dundee , note that eczema “is often cited as the first step in the allergic march.” They say that exposure to peanut proteins in dust through eczema-inflamed skin can trigger a peanut allergy.  How peanut allergies develop is not yet clear, says Dr Carla Davis, a specialist in children’s allergies at Texas Children’s Hospital in Houston in the US. There is still plenty of controversy in the field, she says. For instance, some researchers are testing a “patch” for people who already have a peanut allergy that would introduce the allergen through the skin to build tolerance. That seems to contradict the findings in this study, she says.

The researchers found out how much peanut protein infants were exposed to by measuring dust vacuumed from the patients’ living rooms. They studied 359 children who had a high risk of developing a peanut allergy because they were already allergic to cow’s milk or eggs, or had moderate or severe levels of eczema and had allergies to those foods. “This study adds to the growing body of evidence that exposure to peanut via a damaged skin barrier [as in eczema] may increase the risk of peanut allergy,” Helen Brough says in a news release.

Professor Gideon Lack, senior author from the Department of Pediatrics Allergy, King’s College London, adds: “This is further evidence for the dual-allergen-exposure theory which suggests food allergies develop through exposure to allergens via the skin, likely through a disrupted skin barrier, whilst consumption of these food proteins early in life builds up tolerance in the body. Previous guidelines recommending that mothers should avoid peanuts during  pregnancy and breastfeeding have now been withdrawn. Ongoing studies at King’s aim to find if exposure to solids in early infancy might actually help to prevent allergies. It may be that the timing and balance of skin and oral exposure to a particular food early in life determines whether a child develops an allergy or tolerance to that food.”

Several people involved in the study report receiving support from, or consulting for, pharmaceutical and other companies and organization, including the US National Peanut Board.

Dr. Irena Veksler  of Allergy & Asthma Care of Fairfield County comments: “It has long been known that patients with eczema are at increased risk of food allergies. This study identifies one possible cause of this increased risk, and suggests a possible cause of peanut allergy in particular. More studies are definitely needed.”